1. Field of the Invention
The present invention relates in general to techniques for determining particle coating integrity, and in particular, to a characterization technique for determining the integrity of outer coatings on nuclear fuel particles.
2. Description of the Related Art
In a new design particle bed reactor (PBR), a typical fuel rod consists of millions of tiny multi-layered spherical fuel particles, each having a nominal diameter of roughly about 500 microns (.mu.m). The innermost "kernel" of each particle consists of enriched uranium. The intermediate layers of each particle consist of buffering carbon layers. The outermost layer of each particle consists of a thin coating of a metallic carbide whose primary purpose is to serve as a barrier against escaping fission products. It is readily understood that maintaining the integrity of the fuel particle's outer carbide layer is of the utmost importance.
Currently, there are few inspection techniques applicable to determining the integrity of such particles. Most of these techniques are destructive in nature. Apparatus and methods are also known for acoustic characterization of the integrity of the outer coating on nuclear fuel particles and for differentiating between flawed and unflawed specimen. In these known techniques, the particles to be tested are individually dropped on a piezoelectric acoustic transducer to generate an electrical signal indicative of the integrity of the coating on the dropped particle. Signal analysis is then utilized to evaluate the data showing the acoustic differences between a flawed and unflawed particle by comparing each signal response with that of a calibrated standard of an unflawed particle.
For the apparatus described above, the signal analysis means comprises an amplifier and an analog-to-digital (A/D) converter to amplify the signal and input it into a computer which houses digital analysis software. Differences in the signal response enable discrimination between flawed and unflawed particles. The above method and apparatus is more fully disclosed in U.S. Pat. No. 5,156,802 assigned to the Babcock and Wilcox Company.
From the foregoing it is seen that there exists a need for nondestructive inspection techniques for predicting, prior to particle failure, the integrity of the above discussed nuclear fuel particles which can offer reproducible and reliable results. Prior art techniques rely upon discriminating between failed and unfailed specimen. The present invention offers an avenue to predict whether a given particle or batches of particles will fail if subjected to a given load, without actually subjecting the particles to the destructive load.